Greetings, new...ly returned soul.
<Snipped quote by The Harbinger of Ferocity>
I disagree. People can never be monsters. Whatever they do their actions are the actions of a person. To dismiss them as monsters is to not only dismiss a facet of human nature just because we find it uncomfortable to examine and try to understand, but also helps to absolves them of culpability for what they've done by turning them into something more on the level of an animal.
2. The creature is actively destructive to its ecosystem and/or environment.